Optimization of metal extraction conditions by modified silicas using a factorial design

The extraction properties and the selectivity of silica modified with zirco nium phosphate (SiZrP) and propylimidazol (SiIm) for cadmium, lead and merc ury were evaluated. The optimization of these parameters was carried out by a complete 2(3) factorial design (consisting of two levels and three facto rs), using the intensity of energy dispersive X-ray fluorescence (EDXRF) as response factor. SiZrP adsorbed the three metallic species, while SiIm ads orbed mercury selectively. This difference was assigned to the particular a dsorption process involved in each instance. The interaction factor between pH and silica type was significant, suggesting that an unidimensional stud y could not have optimized the system. Using small amounts of the adsorbent matrices (0.2 g) resulted in better sensitivity, as well as an important s aving of chemicals.